Devices for fastening papers and like objects are well known in the art. There are many different types of paper fasteners including paper clips, staples and brads. Binder clips are also common devices used for keeping papers and the like bound.
For example, FIG. 1 is a perspective view of a prior art binder clip having a triangular cross-section and wire levers. This particular binder clip, shown in FIG. 1, is made by Acco World Corporation. The sidewalls of the clip are spring-biased towards a closed position. The sidewall edges each comprise circular bearings that engage the lever ends and allow the levers to be flipped up such that the clip may be opened, or to be flipped down into a closed position. However, as illustrated in FIG. 4, the upwardly flipped levers are bulky and make it difficult to stack documents one atop the other. The downwardly flipped levers as illustrated in FIG. 5 interfere with bound pages when the pages are flipped or turned, thereby making it difficult for one to read materials bound by the binder clip.
Others have attempted to overcome the problem of cumbersome binder clip levers. FIG. 2 is a top view of a binder clip disclosed in U.S. Pat. No. 1,965,554 (Mainwaring). Mainwaring attempts to solve the problem of the interfering levers by providing a binder clip having solid pivoting levers 1 wherein in a first position, the levers are perpendicular to the longitudinal axis of the clip body and in a second position, the levers are parallel to the longitudinal axis of the clip body. Solid pivoting levers 1 are each secured by a pivot pin comprising a rivet that passes through an upper washer, a keyhole slot in the lever, and then through the flat sidewall of the clip body. This invention suffers from the structural disadvantage of solid levers and a spring catch mechanism used to lock the levers in place. The spring catch mechanism is fixedly secured to the lever by the pivot pin and comprises a spring element having a pocket that engages a steel ball 2, which is forced by the upper washer to matingly engage pivoting lever apertures and apertures in the sidewalls, such as aperture 3. In addition, locking and unlocking the spring catch mechanism strains the pivoting joint causing it to weaken or wear out quickly.
Another patented pivoting lever binder clip is shown in FIG. 3, which illustrates a perspective view of a U-shaped spring binder clip having solid levers 5 attached by a pivoting joint 6 as disclosed in U.S. Pat. No. 467,244 (Ballard). Pivoting joint 6 allows the levers to be pivoted in a backward direction enabling the levers to then open the clip when squeezed, or in a forward direction enabling the bound object to be stored on a shelf without having levers 5 protruding outwardly. To lock each lever in a closed position, a protrusion from the clip's surface catches hole 8 in each lever. A first problem with this design is that it does not have curled edges that engage the lever ends. Therefore, a significant force will be transmitted through the pivoting joint when the levers are squeezed to open the clip causing excessive strain on the pivot. The pivot will further undergo strain when the inflexible solid lever is moved across the protrusion. Additionally, the protrusion from the clip body and the hole in the solid lever must align perfectly, requiring precision in manufacture of the clip.
What is needed, then, is an improved binder clip comprising pivoting levers made of wire and forming a loop, which can sustain significant force when squeezed and which lock into a preferred position by a structurally simple restraining mechanism, wherein protrusions emanating from the clip body wedge into parallel individual segments of the wire levers, thereby allowing one to pivot the levers to lay parallel to the length of the document being bound and out of the way of the reader.